Historically asbestos has been used in asphalt roofing compositions to provide a gelled structure, but environmental concerns have constrained the industry to seek alternative gelling and viscosifying agents. Clay minerals and particularly attapulgite clay minerals have been shown to be effective and are widely used. The attapulgite clays however require the use of cationic surfactants to fully develop the gelling and viscosity properties of the clay.
Cationic surfactants which have been used in this application include quaternary ammonium salts such as Arquad 2C-75 and Arquad T-50 from AKZO Chemicals and Adogen 3690 sold by Witco Chemical. The quaternary salts are corrosive to metal surfaces, and also require relatively high application levels to be effective. They are solid materials at ambient temperatures and are usually diluted with ethanol or isopropanol to render them liquid. The resulting mixtures are flammable which is undesirable in the industries in which they are used. They are water soluble, which may contribute water sensitivity to the final composition, and may also allow them to leach from the asphalt composition creating an environmental hazard.
Also used are alkyloxyalkylamine salts such as PA-14 acetate sold by Tomah Products, Milton, Wis. This product is more effective than the quaternary ammonium salts, but still requires high levels in some applications. This salt is also water soluble.
There is a need for a more efficient surfactant to allow more economical coating compositions. There is also a need for water insoluble surfactants for these applications to eliminate any environmental hazard from leaching of the products from the coating compositions.